Urban Design Tied to Obesity, Diabetes Prevalence

Do 'walkable' neighborhoods bring a health benefit?

People living in neighborhoods deemed more walkable had relatively low levels of obesity and overweight, Canadian researchers said.

In a study of different neighborhoods in the province of Ontario, the prevalence of obesity and overweight was lower in 2001 for the top quintile of walkable neighborhoods than it was for the lowest quintile (43.3% versus 53.5%; P<0.001), reported Maria Creatore, PhD, at St. Michael's Hospital in Toronto, and colleagues.

Creatore and colleagues ranked 8,777 urbanized neighborhoods according to a walkability formula combining population density, the number of walkable destinations, and street connectivity.

"The study by Creatore et al reinforces that urban design for neighborhood walkability is an attractive avenue for public health interventions to reduce the risk of developing obesity or diabetes," wrote Andrew Rundle, DrPH, at Columbia University, and Steven Heymsfield, MD, at Louisiana State University, in an accompanying editorial. "This study will make a prominent contribution to the research base that informs the urban design and health policy debates."

But the authors warned that the "ecologic nature" of the findings, and the finding that walkability wasn't linked to increased physical activity, means that more research is needed to determine whether the association is causal.

In the data, other variables were taken into account as well, like socioeconomic status and whether wealthier residents had displaced poorer ones during the duration that the researchers examined. Languages, the number of houses needing repairs, and the availability of coffee shops and gyms were used to assess socioeconomic status, and the researchers also gathered data about access to parks.

They also examined prevalence of diabetes in certain neighborhoods, broken down by walkability and found that in 2001, the adjusted diabetes incidence was lower in the highest quintile than the other quintiles and declined over the next decade from 7.7 to 6.2 per 1,000 people (absolute change -1.5, 95% CI, -2.6 to -0.4).

On the other hand, diabetes incidence did not significantly change in the least walkable areas:

absolute change -0.65 in quintile 1 (95% CI -1.65 to 0.39)

-0.5 in quintile 2 (95% CI -1.5 to 0.50)

-0.9 in quintile 3 (95% CI -1.9 to 0.02)

Not surprisingly, rates of walking, cycling, and using the public transit were higher in walkable areas, while car use was higher in less walkable areas. However, daily walking and cycling increased only slightly from 2001 to 2011 in the highly walkable areas, and leisure-time physical activity, diet, and smoking status did not vary by walkability (each P>0.05 for quintile 1 versus quintile 5).

"An important consideration in interpreting this study is that the unit of analysis was the area-level prevalence of overweight/obesity and incidence of diabetes over time, by level of neighborhood walkability, not the changes in body weight or the onset of diabetes experienced by individuals followed over this time period," wrote Rundle and Heymsfield.

They added that because of this, the researchers didn't directly measure the effects of a neighborhood, and they didn't look at whether changes in a neighborhood or moving to a new neighborhood mattered to health.

Limitations of the study include the possibility of self-selection -- that healthier people tend to live in more walkable areas. The researchers had to rely on self-reported body mass index and there may have been undiagnosed cases of diabetes. Sixteen residential neighborhoods were excluded from the analysis because of missing census data.

The study was funded by the Canadian Institutes of Health Research.

The authors disclosed no relationships with industry.

Heymsfield disclosed relationships with MediFast, and Rundle disclosed relationships with the American Institute for Architects Designa, Health Research Consortium, and the WELL Building Institute.

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